Rodrigo Duterte, the president of the Philippines, caused shock and sniggers around the world when he called Barack Obama the “son of a whore”. But the Duterte comment that will have really hurt the White House came a few days later. Announcing that he was ending joint naval patrols with the US in the South China Sea, the Philippines’ president stated: “China is now in power and they have military superiority in the region.”

That statement will sting in Washington. Throughout the Obama years, the US has attempted to reassure all its Asian allies that America has both the means and the will to remain the dominant military power in the Asia-Pacific region. President Obama set the tone in a landmark speech in 2011, when he firmly asserted that “the United States is a Pacific power and we are here to stay”. Since then America has transferred more of its navy to the region and Mr Obama has regularly made the long journey from Washington to East Asia.

But Mr Duterte has now directly challenged the idea that America is still the hegemon in the Pacific. If others take his view, power could drain away from Washington, as more countries in the region begin to defer to Beijing.